Everyone who has heard Johnson speak publicly -- including his opponents -- acknowledges his rhetorical talents. But defenders of Darwinism have also turned Johnson's strength into a weakness by suggesting that he argues more like a lawyer than a scientist; he relies, they say, on the verbal tricks of the courtroom to win debates in ways that would never be accepted in the scientific community. Moreover, Johnson makes no bones of the fact that his religious beliefs motivate his attack on Darwinism, throwing the scientific validity of his position into question.

Michael Behe, currently IDT's leading proponent, brings greater intellectual respectability to the movement by means of his impeccable credentials. Behe is a real scientist, with a Ph.D. in biochemistry from the University of Pennsylvania. He worked for four years at the National Institutes of Health studying DNA, then became a teacher at Lehigh University in Bethlehem, Pa., where he is now a full professor of biochemistry. Darwinians who debate Behe can't dismiss him as a crackpot or as a smart but deceptive lawyer. And although Behe is a devout Catholic, he never resorts to theological arguments. Instead, he relies on meticulous reasoning, starting from the detailed biochemical processes that he knows so well, to infer that the observable complexity in living things can only be explained by the existence of an "intelligent designer."

The argument for intelligent design has an appealing, common-sensical simplicity. Suppose a particular person, let's say a woman, dies. Was her death just bad luck, an accident? Or was it the inevitable result of some natural cause, such as bone cancer? Or was she murdered? If we can't plausibly explain the woman's death as accidental or necessary, then we must consider the possibility that she was killed intentionally. Similarly, when we see some complex order in nature that can't be explained as the consequence of chance or necessity, we might infer that it has been caused by an intelligent agent. And if we can't reasonably believe the phenomenon to be the work of some naturally intelligent designer (a human being or an animal), then we might choose to see it as the result of a supernaturally intelligent designer.

Behe, and William Dembski, director of the Michael Polanyi Center at Baylor University in Waco, Texas, were the leading speakers on behalf of a Discovery Institute-sponsored conference last year at Baylor. At least half of the speakers -- including some Nobel Prize-winning scientists -- argued against the theory, while Behe summarized the argument of his 1996 book, "Darwin's Black Box," insisting that Darwinian biology cannot explain those biomolecular mechanisms that are "irreducibly complex." A system is irreducibly complex when it consists of many interacting parts that contribute to some function, such that the removal of any one part prevents the whole system from functioning.

The common mousetrap is Behe's favorite example of an irreducibly complex mechanism. It requires at least five parts -- a platform, a spring, a hammer, a catch and a holding bar -- arranged in a specific way. If one part is missing, or if the arrangement is wrong, the mechanism won't function as a mousetrap. We know that such a device did not arise by chance or by some natural necessity. Instead, it was designed by human intelligent agents with the intention of catching rodent pests. Behe suggested that many biological mechanisms show the same purposeful arrangement of parts found in human devices such as the mousetrap; this, he says, points to an intelligent designer outside of nature.

Maya Angelou reads from "The Heart of a Woman"